The present invention relates generally to a corrosive resistant electronics assembly and more particularly to a corrosive resistant flip chip thermal management structure utilizing a heat sink capable of being used in potted and plastic cased modules.
The design of electronics assemblies must often incorporate a variety of constraints. One of such constraints is the ability to dissipate heat from chips located on the electronics assembly. Chips, such as flip chips, are often mounted on a wide variety of substrates (including ceramic, PCB, flex, etc.). Commonly these chips generate thermal energy that must be dissipated in order for the chips, and the underlying electronic assembly, to function properly and prevent damage. It is known that such heat dissipation may be managed in a variety of methods.
One known method of dissipating heat from a flip chip is accomplished by providing a thermal path from the chip into a ceramic board substrate or into copper traces on a PCB. This is normally accomplished using solder interconnects between the flip chips and the circuitboard and/or by using flip chip underfill. Flip chip underfill provides a thermally conductive path between the flip chip and the board for heat transfer. Using this method, the circuit board is used to dissipate thermal energy into the air inside the case or, if the circuitboard is rigidly mounted to a metal case, the energy may be dissipated through the length of the circuitboard into the metal case. Although this method has been widely used, it is known that heat dissipation using this method is often limited. Therefore, this method, as commonly practiced, may not provide adequate heat dissipation for many applications.
Another known method utilizes a similar technique to that previously described. A thermal path is still used to transfer heat from the flip chip into the circuitboard, however, a module metal case is designed to touch the bottom of the circuitboard and thereby energy passes through the thickness of the board into the module metal case. Thins method of heat dissipation often offers improvements in dissipating power over the previously described method.
A third method of disippating thermal energy from the flip chips involves providing a low thermal resistance contact between the top of the nip chip and a module metal case. This is commonly accomplished through the use of a pedestal located above the flip chip. This method avid similar methods dissipating heat directly from the flip chip into the module metal case can provide further increases in the dissipation of thermal energy.
Although each of the aforementioned methods of heat dissipation have proven useful in a variety of applications, each carries with it disadvantages that leave significant room for improvement. One area where these methods can prove ineffective arises in applications subjected to severe and corrosive environments. Severe and corrosive environments, such as salt spray/salt water immersion environments, may damage metal module cases and therefore make them unsuitable. The use of plastic cases and/or potted controllers to seal the electronics from the corrosive environment can prevent the use of thermal dissipation techniques which previously utilized a metal case as a heat sink. The poor thermal conductivity of plastic and potting material prevents their use as a primary heat sink. Simple dissipation of heat into the circuit board allows for a greater range of casing materials, however its limited thermal dissipation capacity makes this solution unsuitable for many applications. Consequently, an electronics assembly that provided improved heat dissipation characteristics while allowing for use in potted controller situations and/or plastic cases would be highly desirable.
It is therefore an object of tile present invention to provide an electronics assembly with improved thermal dissipation characteristics that may be used in conjunction with potted controllers and/or plastic cases such that it may be used in applications subjected to highly corrosive environments.
In accordance with the object of the present invention, an electronics assembly is provided. The electronics assembly includes at least one chip mounted on a substrate. The chip and substrate are positioned within pottable material to create a corrosive resistant assembly. The electronics assembly further includes a thermally conductive block element positioned within the pottable material and thermally mounted to the chip. Thermal energy generated by the chip is thereby allowed to dissipate from the chip into the thermally conductive block element.